3D fabrication steps

1
3D fabrication steps

• Liam

2
Process order

• Clean sample- common solvent clean
• Deposit SiO2 or Si3N4 using PECVD (plasma
  enhanced chemical vapour deposition)
• Hole formation
• Etch holes
• Dope holes (p- or n-type)
• Deposit SiO2 or Si3N4 using PECVD (plasma
  enhanced chemical vapour deposition)
• Hole formation
• Etch holes
• Dope holes (the other kind)
• Metallise

3
SiO2 layers
PECVD Deposition
RF
Gas mixture silane (SiH4) N2O, N2
Substrate heated to 300o C
4
SiO2 layers
CVD Deposition
5
Etching holes
RIE reactor used to etch SiO2 or Si3N4
ICP reactor used to etch Si
6
Doping the silicon
Diffusion from a solid
Doped glass spun on to substrate
Substrate heated 1000o C
7
Doping the silicon
Diffusion from a solid

• Impurities in dopant
• Higher level of impurities than gas diffusion.
• Thermal process
• Diffusion has dependence on time and temp (D a
  e-kT and units are in cm2s-1)
• Dopant concentration depends on time also,
  allowing more spread of features
• Removal of dopant medium

8
Additive processes

• The most common additive process is lift-off

Developed resist